1. Field of the Invention
The invention relates to a device for locking the end positions of movable railway switch parts, in particular a switch lock, in which two parts capable of being axially displaced relative to each other are displaceable into a position coupled to each other in a positive and force-transmitting manner in at least one moving direction, wherein the relatively displaceable parts are formed by a tube and a rod guided within the tube and are arranged at least partially in a stationary external tube, wherein locking elements comprised of balls cooperate with the axially displaceable parts and the external tube and are displaceable in the radial direction into a lock position into a recess or internal ring groove of the external tube.
2. Prior Art
A device of the above-mentioned kind has already become known from EP-A 603 156, in which locking elements comprised of balls are pressed into their lock positions by means of stops comprised of thickened rod regions, said locking elements in the lock positions lying in a recess of the external tube and on a partial rod region formed with the full diameter. The balls pass through openings of the tubes surrounding the rod and being respectively connected with a tongue such that a relative displacement of that structural part connected with the tongue, i.e., the tube, relative to the external tube will be effectively prevented if the balls are pressed into their outer positions, thus effecting locking between the external tube and the tubular structural part. To undo such a lock, the rod must be displaced, whereby the ball can fall back onto regions having smaller diameters, thus emerging from the lock position within the groove of the external tube.
In the known device only one side, i.e., the closed tongue, was appropriately locked at the line and the correct position of the open tongue was ensured by additional devices such as, for instance, a coupling rod. Such coupling rods, as a rule, are required by the pertinent rail authorities for safety reasons. While, during the displacement movement of the tongue, the forces to be taken up by the ball are limited by the maximum displacement force admissible, the balls may be strained by a multiple in the lock position. Switching forces, as a rule, are in the range of 150 kp, whereas the forces acting on the locking components may be in the range of 10,000 kp and more. Since those locking forces can be taken up by balls only via a line point contact, the points of contact are exposed to an excessively high load, which may lead to inadmissible deformations.
The invention aims to improve the function in a device of the initially defined kind and also guarantee the absorption of extremely high locking forces without the risk of premature impairment of the function of the locking means. To solve this object, the configuration according to the invention essentially consists in that the balls are encompassed by an expandable ring or a ring comprised of segments, that the segments or the ring, respectively, are resiliently held in a position having an outer diameter smaller than, or equal to, the outer diameter of the axially displaceable tube guided within the external tube and are/is immersed in a peripheral groove of the tube, and that the balls are arranged in openings of the tube between the rod and the ring comprised of segments. Due to the fact that the balls no longer directly cooperate with the edges of the grooves of the external tube in the lock position, an extreme load on the edges is avoided and the accordingly high load is taken up by the ring segments or the expandable ring, which, in turn, may have appropriate cross sections in order to ensure surface contact on the side walls of the grooves that are effective for locking. By those segments being resiliently pulled inwards, it is safeguarded simultaneously with a displacement of the rod into a position in which the balls can recede onto a region of reduced cross section, that this radially inwardly directed movement of the balls is assisted by the force of the springs such that, in the following, a minimum displacement resistance between the structural part coupled with the tongue and the external tube will be ensured. To this end, the segments of the ring are immersed in a peripheral groove of the tube with the balls themselves being guided in radial openings of the tube, as in the known configuration.
Advantageously, the configuration is devised such that the ring segments have end faces extending normal to the axial displacement direction or inclined at an acute angle, which end faces cooperate with the stops of the external tube in the lock position so as to ensure the effective and reliable support of high locking forces in the lock position.
In a particularly simple manner, the spring of the ring segments may be constituted by springs extending in the peripheral direction or a spring band. In principle, the individual ring segments may be interconnected by separate springs, wherein a configuration comprising an externally peripheral continuous spring band is particularly simple to produce.
In order to further enhance safety, and not only lock the respectively closed tongue but, at the same time, also be able to lock the respectively open tongue in an appropriate position, the configuration advantageously is devised such that the rod in its end region comprises two axial regions reduced to smaller diameters and an intermediately located axial region having the full diameter, whose axial length is smaller than the distance of two balls neighboring in the axial direction of the tube. With such a configuration, a plurality of planes adjacent in the axial direction may, thus, be utilized as locking planes and a large displacement path with suitable locking of the end positions may be reached at compact structural dimensions. In a particularly advantageous manner, the configuration is devised such that each axially displaceable tube respectively connected with a switch tongue includes openings at an axial distance (l1) which are offset in the axial direction and that the external tube comprises at least two stops so as to be opposed to each other at an axial distance (l2) greater than (l1) and located on a radius exceeding the diameter of the internal tube, the distance (l2) reduced by the distance (l1) corresponding to the axial displacement path between the closed and open end positions of a tongue. With such a configuration, locking of the open tongue by an internally arranged plane of balls and segments, and locking of the tongue being in the abutment position by an externally arranged plane of balls and segments, may each be ensured, wherein it can be safeguarded, at the same time, that the respectively desired direction of locking will be obtained in both cases. In other words, this means that the tongue being in the closed position is secured against moving back into an open position and the tongue being in the open position is secured against moving into the closed position.
The device according to the invention for locking the end positions, at the same time, may be employed as an actuating means for displacing the tongues into the closed position or into the open position. Such a compact displacement actuator may be designed in a particularly simple manner in that the displaceable rod immersing into the tubes is continuously designed over its axial length and in a central region is connected with an actuating means, in particular a piston which is drivable in an axially displaceable manner by fluid within an external tube designed as the cylinder of a double-acting cylinder piston unit. The rod, thus, acts as a piston rod of a double-acting cylinder piston unit and, due to the two rings each arranged to be offset in the axial direction with their respective ring segments and the pertaining balls, one of the thus formed planes may each be utilized for the displacement actuator and/or the lock. In the lock position, the balls rest on a partial region of the rod having the full diameter and, therefore, can in no event be displaced in the axial direction at a displacement of the rod, being locked in the peripheral groove of the external tube. If such an external locking plane consisting of balls and ring segments is subsequently brought into an unlock position by displacement of the rod, those same balls cannot be used for displacement actuation of the tube connected with the tongue, if they abut on the end-side region of the rod. Rather must a stop shoulder of the region, that is located on a larger diameter subsequently seize the internally located balls for displacement actuation and, in this manner, entrain the external tube connected with the tongues over the displacement path of the tongues. That displacement path extends as far as into a wider region of the external tube, in which the balls can again step through outwardly and come out into a new lock position for the then open tongue, the displacement of the tongue out of that opened position being prevented in this manner. As already mentioned, the full-diameter axial region provided in the end region between two reduced to a smaller diameter must have an axial length smaller than the distance of two balls neighboring in the axial direction of the tube in order to safeguard that unlocking has occurred prior to commencing the displacement movement.
Advantageously, the configuration according to the invention is devised such that the external tube on each side of the cylinder comprises a further annular recess between the recess adjacent the cylinder for locking an end position of the tongues and the second recess for locking the opposite end position of the tongues, said further annular recess having a clear width that is smaller than the clear width of the locking recesses for securing the end positions. Such a configuration provides an additional safety if, for instance, the coupling rod has broken. In case of a fracture of the coupling rod, the displacement of an open tongue into the closed position will, in fact, no longer result in the synchronous displacement of the originally closed tongue into an open position, since it was the coupling rod that afforded such a forced coupling. Although the originally closed tongue likewise is moved into an open position by the stop shoulder and the balls, no correct open position will be ensured, which would be obtained only in the presence of a coupling rod. In such cases, the tensile load exerted on the balls becoming active for actuation in that event would suffice to shift those balls together with their ring segments into the further annular recess located therebetween, whereby further displacement is no longer feasible. If, as in accordance with a preferred embodiment of the invention, proximity sensors or displacement path-dependent switches are arranged on or near the cylinder end faces through which the piston rod passes, a signal signalling an incorrect position of the open tongue will be generated, from which a fracture of the coupling rod may be concluded.
In order to ensure the safe function and appropriate sequence of the respective displacement and locking steps, the configuration according to the invention in an advantageous manner is devised such that in an end position of the tongues the distance (l3) of the balls facing the cylinder and resting on a smaller diameter of the rod from the stop formed by the axial region having the full diameter is chosen to be larger than the distance (l4) of the externally located balls of the part of the rod located opposite the cylinder from the stop adjacent those balls and formed by the axial region having the full diameter. In that manner, it is safeguarded that in all cases in which the coupling rod fulfills its function any unintentional emergence of the leading balls into the intermediate recess of the external tube will be avoided and further movement will not be impeded in any manner. Only if the coupling rod has broken will those balls get on the respective counter stop of the region of the rod widening to the full diameter and, thereby, be brought into a position in which further displacement of the rod is no longer feasible, either.
Advantageously, the configuration according to the invention is devised such that in an end position of the rod the axial distance (l5) of the balls resting on the full cross section in their lock position to the end-side region having a smaller diameter of the rod is larger than the distance (l6) of the axially internal balls abutting on the full cross section on the opposite end of the rod from the internally arranged stop formed by the full cross section of the rod. Such a configuration allows for the desired sequence of movement, with the open tongue being unlocked first and then lock of the closed tongue being undone afterwards.
Advantageously, the axial width of the externally locked locking grooves of the external tube is larger than the axial width of the ring comprised of segments, thereby ensuring the safe entry of the segments under the pressure of the locking members, into the lock position of the external tube.
The device according to the invention, with minimal modifications and the use of largely identical structural parts, is suitable also for an embodiment in which the railway switch is trailable. In this case, a first unit facing away from the tongue end must be designed such that it can be opened under the force of the rolling load, wherein a suitable hydraulic coupling is able to undo the lock of the consecutive units. In this case, the configuration advantageously is devised such that, with the arrangement of a plurality of devices for locking the end positions acting in a spaced-apart relationship in the longitudinal rail direction, at least one device comprises locking elements capable of being displaced against the force of a spring and of being shifted outwards following a predetermined displacement path in the axial direction under the compression of the spring in the radial direction, releasing the further displacement path of the rod, and that the fluid volumes of the cylinder piston units of neighboring devices are interconnected to a piston displacement in same direction. Unlocking of that first unit facing away from the tongue end by overcoming the force of the spring, by fluid being pressed out into the respective working volumes of further units arranged in the direction towards the tongue end, results in the hydraulic unlocking of also those units, thus enabling resetting or switching by the rolling load when approaching the switch. The definitive lock of such a railway switch reset after approaching, however, must again be ensured by the appropriate hydraulic actuation of the rods in order to reliably reach the respectively required end position.
In a particularly simple manner, the configuration in those cases is devised such that the springs are designed as helical springs concentrically surrounding the piston rod and supported between the end walls of the cylinder piston unit and one spring plate each being displaceable within the external tube against a stop of the external tube, wherein the spring plate, which is displaceable within the external tube, in a manner distributed about its periphery carries balls that are radially displaceable in radial openings of the spring plate. Such a spring plate carrying the balls displaceable in the radial direction ensures that the compression stroke extends over a limited course only and, as a result, the free displaceability of the rod and hence complete unlocking are safeguarded. To this end, the balls in their spring plates are shifted into a radially outward position in which the spring need not be further compressed for further displacement of the rod.
The entrainment of the respective closed tongue into the open position is effected during approaching by displacement forces entering into action on the open tongue. In this embodiment, which relates to the switch regions that are located the farthest remote from the tongue ends, no additional tie rod or coupling rod is provided, as a rule, coupling rods usually being arranged near the switching actuator itself. Thus, in order to effect the displacement of the closed tongue into the open position without the wheel flange having to press open the closed tongue for that purpose, the configuration advantageously is devised such that the rod cooperating with axially acting springs on its end-side end faces carries a head having a diameter exceeding the diameter of the rods, which head cooperates with axially external stops of the tube.